Sign Up
School Account Sign Up
Contributor: Elephango Editors. Lesson ID: 10818
Ever wondered how scientists figure out the age of ancient fossils or artifacts? Dive into the science of carbon dating and discover how this method unlocks the mysteries of the past!
Could a Fossil Be Faking Its Age?
Imagine you’re holding a fossilized leaf.
Scientists claim to know, but they’re not using a giant stopwatch or flipping through a fossil birth certificate. They’re using radioactive dating, a scientific method that measures invisible particles to determine how long something has been around.
Now here’s the catch: not everyone agrees on how reliable this method is. Some believe the earth is extremely old, while others aren’t so sure.
This lesson won’t try to convince you either way. Instead, you will explore the facts, learn how radioactive dating actually works, and decide what you think based on real science.
What Is Radioactive Dating?
Radioactive dating is a method scientists use to estimate how long ago something, like a rock, bone, or once-living organism, stopped interacting with the atmosphere.
It's based on the idea that some atoms are unstable and break down, or decay, over time. When they do, they release particles and turn into different atoms at a rate that scientists can measure.
That steady rate of decay is what makes radioactive dating possible.
One of the most well-known types of radioactive dating is carbon-14 dating. This method is used on things that were once alive, like plants, animals, or even people. Here's how it works.
How Carbon-14 Dating Works
In the earth's atmosphere, cosmic rays (high-energy particles from space) constantly collide with atoms. These collisions cause nitrogen atoms to transform into a rare form of carbon called carbon-14, which is radioactive.
Carbon-14 mixes with oxygen to form carbon dioxide, which plants then absorb during photosynthesis. When animals eat the plants (and we eat the animals), carbon-14 enters the food chain—and eventually, your body.
As long as something is alive, it keeps taking in carbon-14. But once it dies, it stops.
From that point on, the carbon-14 in its body starts to decay. It turns back into nitrogen over time and does this at a predictable pace, cutting in half every 5,730 years. This is known as its half-life.
By measuring the amount of carbon-14 left in a sample compared to how much would have been there when it was alive, scientists can estimate how long it's been since that living thing died.
What It Can—and Can't—Tell You
Carbon-14 dating works best on things less than 50,000 years old. That means it's useful for studying things like ancient tools, bones, or preserved plants.
It doesn't work well on rocks or anything millions of years old—that's when scientists use different methods involving other radioactive materials like uranium or potassium.
It's also important to know that carbon dating makes a few assumptions.
That the amount of carbon-14 in the atmosphere has stayed mostly constant.
That the object being tested hasn't been contaminated by other sources of carbon.
That scientists know what the original amount of carbon-14 was when the organism died.
Because of these assumptions, not everyone agrees on how accurate the results always are. That doesn't mean the method is useless—it just means it's one tool among many, with limits.
In science, it’s okay to ask questions—that’s part of how progress is made.
Up Next: Can You Figure It Out?
Now that you've got the basics, it's time to test your understanding.
Head to the Got It? section to break down a few scenarios and try some practice questions to see radioactive dating in action. See what you've picked up so far!
Supplies
FAVORITE
Like